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The Payload Flattener

A medium Python interview practice problem on DataDriven. Write and execute real python code with instant grading.

Domain
Python
Difficulty
medium
Seniority
junior, mid, senior

Problem

Our product catalog API returns deeply nested JSON, but the warehouse expects flat rows with no nesting. Write a function that takes a nested dictionary and produces a flat one where keys from different levels are joined with a separator. No libraries allowed.

Practice This Problem

Solve this Python problem with real code execution. DataDriven runs your Python code in a sandboxed Docker environment and grades it instantly.